INSIDE HARDWARE
Computers are made of many electronic components or parts. These components each have a special job and they all work together to make your computer operate. Some components are hidden inside the computer where you can't see them. Others can be seen partly from the outside.
Every computer needs a power supply to take electricity from your house and convert it into a current that works for your computer. The electrical cord that comes out of your computer comes out of the power supply. When it is plugged into the wall, electricity travels from the electrical wires in your house into the computer's power supply. When your computer is turned on, the power supply allows the converted electricity to travel to other components inside the computer.
The motherboard gets its name because it is like a mother to all of the
other circuit boards. Found at the bottom of a desktop case or the side of a
tower case, the motherboard is the largest circuit board and has many smaller
boards plugged into it. It holds all of the most important parts of the
computer.
On the motherboard, you will find several expansion cards. Each of these cards has a special purpose. The sound card contains special circuits for operating the computer's sound. The video card handles graphics that are displayed on the monitor. There are also expansion cards for other computer components including the drives and ports.
The modem is an expansion card that allows computers to talk to each other. A modem plugs the computer in to a phone or cable line so that information can be transferred between computers. Current modems can run up to 56,000 bits per second. Don't know what a bit is? Don't worry, we'll get to that in a later lesson
The brain of a computer is the CPU or Central Processing Unit. Like a brain, it controls information and tells other parts what to do. The type of CPU in a computer also determines how fast that computer can operate. A CPU generates lots of heat, so there is usually a small fan nearby to cool it down.
A very important computer component is the BIOS chip. BIOS stands for Basic Input Output System. In very simple terms, the BIOS chip wakes up the computer when you turn it on and reminds it what parts it has and what they do.
Have you ever heard the terms RAM and ROM? These two terms sound
very similar and can easily be confused by beginners. However, understanding
what they mean and what they do can help you to remember.
RAM stands for Random Access Memory. RAM chips will remember what you tell them and can even change to remember new information. But, when the computer is turned off, RAM forgets everything you told it. This is why it is so important to save your work on a computer - if the computer gets turned off, RAM will lose all of your work!
ROM stands for Read Only Memory. ROM is good at remembering, but cannot change it's mind. It holds information that is built into it. ROM is like reading a library book - lots of information is there, but you can't change it (because you never write in a library book). RAM, on the other hand, is more like a journal - you can write information into the journal. But if you change your mind, you can erase and write in new information.
Ports are the places on the outside of the computer case where you plug in hardware. On the inside of the case, they are connected to expansion cards. The keyboard, mouse, monitor, and printer all plug into ports. There are also extra ports to plug in extra hardware like joysticks, gamepads, scanners, digital cameras and the like. The ports are controlled by their expansion cards which are plugged into the motherboard and are connected to other components by cables - long, flat bands that contain electrical wiring.
Disk drives read information off of storage disks. The three most common disk drives are the hard drive, floppy disk drive and CD-ROM. In lesson 1, you learned a bit about the latter two, which are usually installed inside the front of your computer case so that you can get to them from the outside to load the software. The hard drive, however is hidden inside the computer because the disks are not meant to be removed. Information that you save on your computer is stored on these hard disks. You can learn more about storage disks in Lesson 4: Storage; but first, check out Lesson 3 to learn about bits and bytes.
STORAGE
The purpose of storage in a computer is to hold data or information and get that data to the CPU as quickly as possible when it is needed. Computers use disks for storage: hard disks that are located inside the computer, and floppy or compact disks that are used externally.
Your computer uses two types of memory: primary memory which is stored on chips located on the motherboard, and secondary memory that is stored in the hard drive. Primary memory holds all of the essential memory that tells your computer how to be a computer. Secondary memory holds the information that you store in the computer.
Inside the hard disk drive case you will find circular disks that are made from polished steel. On the disks, there are many tracks or cylinders. Within the hard drive, an electronic reading/writing device called the head passes back and forth over the cylinders, reading information from the disk or writing information to it. Hard drives spin at 3600 or more rpm (Revolutions Per Minute) - that means that in one minute, the hard drive spins around over 3600 times!
Today's hard drives can hold a great deal of information - sometimes over 20GB!
The process of reading and writing to a hard disk is done with electricity and magnetism. The surfaces of this type of disks can be easily magnetized. The electromagnetic head of the disk drive records information to the disk by creating a pattern of magnetized and non-magnetized areas on the disk's surface. Do you remember how the binary code uses on and off commands to represent information? On the disk, magnetized areas are on and non-magnetized areas are off, so that all information is stored in binary code. This is how the electronic head can both write to or read from the disk surface.
It is very important to always keep magnets away from your computer! The magnets can erase information from the hard disk!
Instead of electromagnetism, CDs use pits (microscopic indentations) and lands (flat surfaces) to store information much the same way hard disks use magnetic and non-magnetic storage. Inside the CD-ROM is a laser that reflects light off of the surface of the disk to an electric eye. The pattern of reflected light (pit) and no reflected light (land) creates a code that represents data.
CDs usually store about 650MB. A DVD or Digital Video Disk holds even more information than a CD, because the DVD can store information on two levels, in smaller pits or sometimes on both sides.
You might wonder: If all the information is stored safely inside my computer, why would I need to store it outside? There are several reasons why portable storage is so important.
CDs and other kinds of external memory make it possible to backup important information in case it is lost by the computer. Do you remember in Lesson 2, we talked about RAM and ROM? RAM loses its memory each time the computer is turned off, but ROM keeps information stored even when the computer is not turned on. Well, sometimes computers have problems that can cause them to crash. No, that doesn't mean they jump off the desk and smash on the floor. A crash is something that happens inside the computer's circuits and can make it forget things. Some crashes can even make ROM forget everything! Having important information backed up on disks will allow you to put it back into your computer's memory. Backup disks can save you lots of time and headaches.
Disks also allow information to be transferred between different computers. Let's say that you are working on a project using a computer at the library, but you don't finish it by closing time. There's your project sitting in the computer. How do you get it home to finish it on your computer? You write the information to a disk, take it home and upload the information into your computer from the disk. What an easy way to transfer information!
The most common use for compact discs (aside from playing music) is storage of software programs. When you purchase a computer game, the program that tells your computer how to run the game is stored on a CD. You move the program into your computer's memory by installing it. Some programs are transferred completely into your computer's hard drive. However, many programs are very large and would take up lots of memory space on your hard drive. To keep that from happening, these programs are designed to only upload part of the program onto your computer. The rest of the program stays on the software disk. The program cannot be run from your computer unless you have the CD in the disc drive so that RAM can read the rest of the program from it.
With the introduction of CD-RW (disc drives that can write to compact discs as well as read from them), CDs can now be used for storage. Using a CD-RW, computer data can be backed up to a CD. All kinds of information can now be saved on CD. Many people store music files or family photos on CD.